This work continues our studies of the enzymatic catalysis of the methylation and acetylation of endogenous biogenic amines by brain tissue. Both chemical reactions may be implicated in processes by which normal endogenous neurotransmitters are converted into a more or less active form. These kind of biotransformations have been suggested to be of potential significance in the biochemistry of some mental illnesses. BIBLIOGRAPHIC REFERENCES: Hsu, L. and Mandell, A. "Enzymatic Formation of Tetrahydro-beta-Carboline from Tryptamine and 5-Methyltetrahydrofolic Acid in Rat Brain Fractions: Regional and Subcellular Distribution." Journal of Neurochemistry 24: 631-636 (1975). Hsu, L., Geyer, M., and Mandell, A. "Extrapineal Amine N-Acetylation in Rat Brain: Regional and Subcellular Distribution and Enzyme Kinetics." Biochemical Pharmacology, in press (1975).